1. Field of the Invention
This invention relates to a method or apparatus for controlled or regulated charging, discharging, or combined charging and discharging of one or more voltaic cells, batteries, or capacitors. Specifically, this invention relates to a multi-battery system for high-voltage applications with proportional power sharing.
2. Description of the Prior Art
A number of operationally critical applications have power requirements that require high voltages and currents and require a high degree of availability and reliability. One way of ensuring high reliability is to have a high degree of redundancy in as many components of the system as possible. In battery operated systems the most critical component is often the batteries and in high voltage applications a large number of batteries may be required to produce the necessary power output. For example, in an uninterruptible power supply (UPS) the system relies on multiple batteries feeding a voltage converter system that increases the system voltage. The UPS relies upon switched mode power supplies formed from inductors, capacitors and other elements in order to convert an incoming DC voltage to an output DC or AC voltage. In cases where redundancy is required, multiple batteries and multiple voltage converters are used to provide power in the event that a single system element fails. The requirement for redundancy can result in very large and unwieldy systems due to the duplication and even triplication of system components. Where multiple battery banks are relied upon to supply an input voltage the system may not share the charge equally between battery banks. This results in one battery bank or one voltage converter supplying the majority of the standby power. Ideally, the system should be able to determine which battery bank has the highest state of charge in order to supply the most reliable input voltage. The inability to do so may result in the UPS continually relying upon a depleted battery bank for input voltage. Overtime, the depleted batteries will fail to charge and the UPS becomes less reliable.
To partially overcome this design deficiency power systems relying upon multiple batteries power share between them. This results in equal power consumption from each battery. However such systems can still fail to take into account the state of charge of the batteries. This will result in a depleted battery continually being called upon to share a load it is not capable of producing. In the end, the battery will fail and the system reliability will be compromised.
Another situation can occur in very large power systems where perhaps hundreds of batteries are used. Individual batteries or groups of batteries can be “hot-swapped”. This results in the battery bank containing both older and new batteries having a variety of charge states and reliabilities. Overall, system reliability is reduced. In this situation, a system that is able to detect the state of charge of a battery or battery bank and rely upon the most fully charged batteries to supply input voltage would ensure longer battery life and a greater UPS reliability.
Therefore, in light of the deficiencies in UPS systems noted above, there is a need for a multi-battery system that provides redundant input voltage without the expense and bulk of duplicated or triplicate critical components.